In general, the low dynamic stiffness of engine mount is good for the idle state or low-speed driving of a vehicle, and the large dynamic stiffness of engine mount is good for a high-speed driving.
The conventional hydraulic engine mount has a housing sealed with liquid at a lower portion of a rubber elastic body performing a first shock-absorbing function. The inside of the housing is divided into a top fluid chamber and a bottom fluid chamber by a dividing means installed therein, and in the dividing means is formed one fluid-moving channel through which fluid can move between the bottom fluid chamber and the top fluid chamber. By changing the dynamic stiffness of engine mount through opening and closing of the fluid-moving channel it enables to reduce vibrations of frequency range generated from the engine during an idle state or low-speed driving and vibrations of frequency range generated from the engine during an high-speed driving as effectively according to frequency as possible, but it could not make peak damping around two corresponding frequency ranges.
Especially, an engine mount is being developed, which can reduce vibration more efficiently in each corresponding frequency by changing the dynamic stiffness of the engine mount through opening and closing the one fluid-moving channel or the air track connected with the atmosphere in an ignition mode (7˜8 Hz) and the rough road driving mode (11˜13 Hz) in a vehicle having a function of stop/start, but an engine mount has not been developed yet, which has an excellent damping property in both the ignition mode (7˜8 Hz) and the rough road driving mode (11˜13 Hz).
Since the above conventional engine mount has only one fluid-moving channel, it is impossible to make a large variation of peak damping frequency according to opening and closing of the fluid-moving path. That is, the conventional engine mount cannot reduce vibration efficiently in each of different modes, and cannot form peak damping frequency ranges tuned accurately to the frequency corresponding to the ignition mode (7˜8 Hz) and the rough road driving mode (11˜13 Hz). Thus the conventional engine mount compromises fittingly in evaluating a vehicle and developing process of engine mount, and sets the peak damping frequencies to 8 Hz and 10 Hz or 9 Hz and 11 Hz, for example. Therefore, the conventional engine mount achieves some vibration reduction effect in a single mode, but the vibration reduction capability in other modes is decreased.
Also, since the conventional engine mount has only one fluid-moving path and thus performs the damping function only with states of closing and opening upper and lower fluid chambers completely, it is difficult to have it perform peak damping according to various frequency ranges.